1. Technical Field
The present disclosure relates to flexible printed circuit boards (FPCBs) and, particularly, to an FPCB for transmitting high speed signals.
2. Description of Related Art
FPCBs are light, soft, thin, small, ductile, flexible, and supporting high wiring density. FPCBs can be three-dimensionally wired and shaped according to space limitations. Flexible circuits are generally useful for electronic packages where flexibility, weight control and the like are important.
Referring to FIG. 1, a related-art FPCB includes a signal layer and a ground layer 50. A differential pair 51 consisting of two transmission lines 52 and 54 is arranged in the signal layer. The ground layer 50 is beneath the signal layer and etched in a grid array. The layout in the ground layer 50 beneath the transmission line 52 is different from that beneath the transmission line 54, noise is easily generated, which prevents the FPCB from transmitting high speed signals.